Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271847 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 247 PM EDT SUN JUL 27 2014 .SYNOPSIS...
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LOW PRESSURE OVER MICHIGAN IS EXPECTED TO TRACK ACROSS PENNSYLVANIA TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND DRIER CONDITIONS DURING MIDWEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SEVERE WEATHER IS EXPECTED FOR THE MID ATLANTIC TODAY AND TONIGHT. A POTENT SHORTWAVE TROUGH IS MOVING ACROSS THE WESTERN GREAT LAKES WHILE A SFC LOW RESIDES JUST AHEAD OF IT OVER SRN MI THIS AFTERNOON. AN ASSOCIATED COLD FRONT EXTENDS FROM MI THROUGH IN/KY. AHEAD OF THIS COLD FRONT...SOUTHERLY WINDS HAVE LED TO DEWPTS TO CLIMB AROUND 70 DEG F IN THE MID-ATLANTIC. A FEW DISTURBANCES HAVE CROSSED THE REGION TODAY CAUSING A CHAOTIC CLOUD DECK RESULTING IN SOME AREAS WARMING FASTER THAN OTHERS. THIS INCLUDES NRN MD AND THE POTOMAC HIGHLANDS. TEMPS RANGE FROM THE MID TO UPPER 80S IN THIS AREA TO THE UPPER 70S NEAR CHO. PER THE MESOANALYSIS...INSTABILITY HAS RISEN TO 1K-2K J/KG ACROSS THE REGION WITH 2K-3K J/KG NEAR THE MASON DIXON LINE WHERE MOST OF THE HEATING HAS OCCURRED. 0-6 KM SHEAR HAS INCREASED TO 40-50 KTS. THE EXIT REGION OF THE JET STREAM IS STILL BACK ACROSS THE OHIO VALLEY BUT WILL MOVE EASTWARD THIS AFTERNOON. THUNDERSTORMS ARE EXPECTED TO MOVE FROM OHIO AND TRACK E-SE INTO THE MID-ATLANTIC LATE THIS AFTERNOON. CONDITIONS WILL CONTINUE TO BECOME MORE UNSTABLE AND SUITABLE FOR STRONG THUNDERSTORM DEVELOPMENT ACROSS THE MID ATLANTIC THIS AFTERNOON. ADDITIONAL THUNDERSTORMS WILL LIKELY FORM ON OUTFLOW BOUNDARIES IN THE OHIO VALLEY AND MOVE EASTWARD BY THIS EVENING. EXPECT THUNDERSTORMS TO CROSS THE APPALACHIANS LATE THIS AFTERNOON REACHING THE I-95 CORRIDOR THIS EVENING. SUPERCELLS ARE EXPECTED AND WILL LIKELY LEAD TO DMG WINDS...LARGE HAILS...ISOLATED TORNADOES AND HEAVY RAINFALL. AT THIS TIME FFG IS HIGH AND PWATS ARE MARGINAL. FLASH FLOODING IS ALWAYS A CONCERN WITH THUNDERSTORMS THAT MOVE OVER THE SAME REGION AND THEREFORE IT IS POSSIBLE THIS EVENING. SHOWERS MOVING ACROSS THE CENTRAL FOOTHILLS THIS AFTERNOON HAVE BEEN IN AN UNFAVORABLE ENVIRONMENT FOR THUNDERSTORMS DUE TO THE LOWER INSTABILITY...AT THIS TIME. THEY ARE TRACKING INTO A FAVORABLE AREA AND WILL BE MONITORED CLOSLY. THE POTENT SHORTWAVE TROUGH WILL MOVE ACROSS LAKE ERIE LATE TONIGHT WHILE THE COLD FRONT CROSSES THE MID ATLANTIC. WESTERLY WINDS WILL MOVE IN BEHIND THE COLD FRONT AND THUNDERSTORMS WILL MOVE EAST OF THE BAY BY EARLY MONDAY MORNING.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
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THE TROUGH WILL BE OVER NY MONDAY AND WHILE THE COLD FRONT WILL BE OFF THE COAST. AS ENERGY ROUNDS THE BASE OF THE TROUGH MONDAY SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE MAINLY I-66 AND NORTH MONDAY AFTERNOON. NW WINDS WITH GUSTS UP TO 30 MPH WILL BE POSSIBLE IN THE AFTERNOON. FCST MIN TEMPS MONDAY NIGHT RANGE FROM THE MID 50S IN THE HIGHLANDS TO THE LOW 60S NEAR THE METROS AND WATERS. NRLY WINDS WIL CONTINUE TUESDAY AND TEMPS WILL ONLY RISE INTO THE UPPER 70S WHICH WILL FEEL LIKE A FALL DAY FOR THE MID-ATLATNIC.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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MEAN TROUGHING WILL PERSIST ALOFT OVER THE EASTERN CONUS THROUGH THE REMAINDER OF THE UPCOMING WEEK. DRY AIR AND NORTHWEST FLOW AROUND HIGH PRESSURE AT THE SURFACE WILL KEEP THE REGION DRY AND COOLER THAN NORMAL DURING THIS PERIOD. MODELS INDICATE THE TROUGH AXIS WILL SLOWLY RETROGRADE BACK WEST OF THE AREA LATE IN THE WEEK INTO NEXT WEEKEND AS SUBTROPICAL RIDGING RE-ESTABLISHES ITS HOLD OVER THE WESTERN ATLANTIC. AS THE TROUGH MOVES BACK/REDEVELOPS TO OUR WEST...WINDS WILL BECOME SOUTHERLY INCREASING THE HEAT AND HUMIDITY AS WELL AS THE CHANCES OF SHOWERS AND THUNDERSTORMS. THE LONGWAVE PATTERN BY THE END OF NEXT WEEKEND WOULD SUGGEST A POTENTIAL FOR HEAVY RAIN GIVEN THE LONG AND PERSISTENT TRAJECTORY OF WIND OUT OF THE GULF OF MEXICO RIDING ALONG A STALLED OR SLOW-MOVING FRONT.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON. COVERAGE WILL INCREASE THIS EVENING AND LIKELY IMPACT THE TERMINALS. MVFR/IFR IS LIKELY IN THUNDERSTORM ACTIVITY. SOME THUNDERSTORMS ARE EXPECTED TO BE STRONG TO SEVERE RESULTING IN STRONG WINDS...LARGE HAIL AND ISOLATED TORNADOES. HEAVY RAIN WILL ALSO CAUSE LOW VSBYS. THIS ACTIVITY ALL AHEAD OF A COLD FRONT WILL MOVE FROM WEST TO EAST TONIGHT. ACTIVITY SHOULD BE THROUGH MRB THE EVENING TO THE DCA-BWI-MTN BY MIDNIGHT. N-NW WINDS WILL MOVE IN BEHIND THE FRONT MONDAY. SHRA AND -TSRA IS POSSIBLE MONDAY AS ENERGY MOVES ACROSS THE AREA. NW WINDS AROUND 10-15KTS WITH GUSTS UP TO 25KTS EXPECTED AT THE TERMINALS. NW FLOW GENERALLY 10 KTS OR LESS W/ VFR TUE-THU.
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&& .MARINE...
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S-SW FLOW EXPECTED ON THE WATERS THIS AFTERNOON AND EVENING. SHOWERS AND THUNDERSTORMS ARE EXPECTED LATE TONIGHT AND INTO MONDAY MORNING AHEAD OF A COLD FRONT. WINDS WILL BECOME NWLY MONDAY. A SCA IS IN EFFECT FOR THE WATERS THIS AFTERNOON. PORTIONS OF THE UPPER TIDAL POTOMAC AND CHESAPEAKE BAY WILL DROP LATE TONIGHT. A SCA IS IN EFFECT FOR ALL THE WATERS MONDAY. RELATIVELY BENIGN SURFACE PRESSURE GRADIENT WITH HIGH PRESSURE NEARBY OR OVERHEAD TUE NIGHT-FRI IS EXPECTED TO RESULT IN SUB-SCA CONDITIONS ON THE WATERS. WINDS BECOME SOUTHERLY AND INCREASE NEXT WEEKEND...POSSIBLY TO SCA LEVELS BUT THAT IS UNCLEAR THIS FAR OUT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ530-531- 535-536-538-539-542. SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530- 531-535-536-538-539-542. SMALL CRAFT ADVISORY UNTIL 7 PM EDT MONDAY FOR ANZ532>534-537- 540-541-543.
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&& $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...HAS LONG TERM...DFH AVIATION...HAS/DFH MARINE...HAS/DFH

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